package com.learn.algorlthm;

/**
 * @classname:
 * @Description: 合并两个排序的链表
 * @author: yfpu(fengpu.yang @ ucarinc.com)
 * @Date: 2018-07-27 13:38
 */
public class Learn25 {

    //递归
    public static ListNode merge(ListNode list1, ListNode list2){
        if (list1 == null)
            return list2;
        if (list2 == null)
            return list1;

        if (list1.val < list2.val) {
            list1.next = merge(list1.next, list2);
            return list1;
        } else {
            list2.next = merge(list1, list2.next);
            return list2;
        }

    }

    //迭代
    public static ListNode merge_2(ListNode list1, ListNode list2) {
        if (list1 == null)
            return list2;
        if (list2 == null)
            return list1;

        ListNode returnListNode = new ListNode();
        ListNode cur = returnListNode;

        while (list1 != null && list2 != null) {
            if (list1.val < list2.val) {
                cur.next = list1.next;
                list1 = list1.next;
            } else {
                cur.next = list2.next;
                list2 = list2.next;
            }
            cur = cur.next;
        }

        if (list1 != null)
            cur.next = list1;
        if (list2 != null)
            cur.next = list2;

        return returnListNode.next;
    }



    static class ListNode {
        public int val;
        public ListNode next;
    }

}
